Investigation of soil improvement by deep mixing method using laboratory tests and finite elements method

Today, in cases where the soil not suited for superstructure construction, soil improvement is carried out using various improvment methods. With the advancement of technology, numerous improvement methotds have been used. The deep mixing method is the process of on site soil improvement by mixing it with different binders homogeneously using high pressure. Cement is generally used as binder, and binders such as calcitic, fly ash, blast furnace cinder are also used. It is aimed to reduce environmental pollution and to obtain more economical results by using fly ash in soil improvement methods. For this reason, fly ash, which is a waste material, was preferred in the selection of binder material.Within the scope of this thesis, CL class low plasticity, 30% water content soil was modeled in the laboratory using cement and fly ash. 5%, 10%, 15% cement and 2.5% cement + 2.5% fly ash, 5% cement + 5% fly ash, 7.5% cement + 7.5% fly ash were used of the dry weight of the clay. Sieve analysis, hydrometer analysis, liquid limit and plastic limit tests were applied to determine the parameters of the clay soil. Columns were formed with a deep mixing mechanism and wet deep mixing method. The 7, 14, 28, 45 and 60 day strengths of the obtained samples were obtained by performing uniaxial unconfined compression tests. The parameters of the deep mixing columns were determined with the help of the free compressive strengths and correlations that were obtained as a result of the experiments and analyzed with PLAXIS 2D. As a result of uniaxial pressure tests, the highest strength in cement-containing samples is 3025.37 kPa at 15% cement content. As a result of tests, it was observed that only cement samples ob tained higher strenght in less curing time. KEYWORDS: Deep mixing method, uniaxial unconfined compression test, fly ash